Re: [PATCH v3] ui: Print available display backends with '-display help'

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 1/8/20 3:47 PM, Thomas Huth wrote:
> We already print availabled devices with "-device help", or available
> backends with "-netdev help" or "-chardev help". Let's provide a way
> for the users to query the available display backends, too.
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   v3: Mention -display help in the qemu-doc, too (as suggested by Philippe)
> 
>   include/ui/console.h |  1 +
>   qemu-options.hx      |  3 ++-
>   ui/console.c         | 15 +++++++++++++++
>   vl.c                 |  5 +++++
>   4 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/include/ui/console.h b/include/ui/console.h
> index 281f9c145b..f35b4fc082 100644
> --- a/include/ui/console.h
> +++ b/include/ui/console.h
> @@ -442,6 +442,7 @@ void qemu_display_register(QemuDisplay *ui);
>   bool qemu_display_find_default(DisplayOptions *opts);
>   void qemu_display_early_init(DisplayOptions *opts);
>   void qemu_display_init(DisplayState *ds, DisplayOptions *opts);
> +void qemu_display_help(void);
>   
>   /* vnc.c */
>   void vnc_display_init(const char *id, Error **errp);
> diff --git a/qemu-options.hx b/qemu-options.hx
> index e9d6231438..d593931664 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1586,7 +1586,8 @@ STEXI
>   @item -display @var{type}
>   @findex -display
>   Select type of display to use. This option is a replacement for the
> -old style -sdl/-curses/... options. Valid values for @var{type} are
> +old style -sdl/-curses/... options. Use @code{-display help} to list
> +the available display types. Valid values for @var{type} are

Nicer, thanks!

>   @table @option
>   @item sdl
>   Display video output via SDL (usually in a separate graphics
> diff --git a/ui/console.c b/ui/console.c
> index ac79d679f5..69339b028b 100644
> --- a/ui/console.c
> +++ b/ui/console.c
> @@ -2333,6 +2333,21 @@ void qemu_display_init(DisplayState *ds, DisplayOptions *opts)
>       dpys[opts->type]->init(ds, opts);
>   }
>   
> +void qemu_display_help(void)
> +{
> +    int idx;
> +
> +    printf("Available display backend types:\n");
> +    for (idx = DISPLAY_TYPE_NONE; idx < DISPLAY_TYPE__MAX; idx++) {
> +        if (!dpys[idx]) {
> +            ui_module_load_one(DisplayType_str(idx));
> +        }
> +        if (dpys[idx]) {
> +            printf("%s\n",  DisplayType_str(dpys[idx]->type));
> +        }
> +    }
> +}
> +
>   void qemu_chr_parse_vc(QemuOpts *opts, ChardevBackend *backend, Error **errp)
>   {
>       int val;
> diff --git a/vl.c b/vl.c
> index 86474a55c9..ee15055ba2 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1869,6 +1869,11 @@ static void parse_display(const char *p)
>   {
>       const char *opts;
>   
> +    if (is_help_option(p)) {
> +        qemu_display_help();
> +        exit(0);
> +    }
> +
>       if (strstart(p, "sdl", &opts)) {
>           /*
>            * sdl DisplayType needs hand-crafted parser instead of
>